Modeling the dynamic characteristics of pneumatic muscle

• Published in: Annals of biomedical engineering Vol. 31; no. 3; pp. 310 - 317
• Main Authors: Reynolds, D B, Repperger, D W, Phillips, C A, Bandry, G
• Format: Journal Article
• Language: English
• Published: United States Springer Nature B.V 01.03.2003
• Subjects: Air Pressure; Animals; Artificial Organs; Biomedical engineering; Biomimetic Materials; Biomimetics - instrumentation; Biomimetics - methods; Coefficients; Computer Simulation; Damping; Dynamical systems; Dynamics; Elasticity; Humans; Mathematical models; Models, Biological; Models, Theoretical; Motion; Muscle Contraction - physiology; Muscle, Skeletal - physiology; Perturbation methods; Rheology - instrumentation; Rheology - methods; Robotics - instrumentation; Robotics - methods; Springs; Springs (elastic); Stress, Mechanical; Viscosity
• ISSN: 0090-6964; 1573-9686
• DOI: 10.1114/1.1554921

A pneumatic muscle (PM) system was studied to determine whether a three-element model could describe its dynamics. As far as the authors are aware, this model has not been used to describe the dynamics of PM. A new phenomenological model consists of a contractile (force-generating) element, spring element, and damping element in parallel. The PM system was investigated using an apparatus that allowed precise and accurate actuation pressure (P) control by a linear servo-valve. Length change of the PM was measured by a linear potentiometer. Spring and damping element functions of P were determined by a static perturbation method at several constant P values. These results indicate that at constant P, PM behaves as a spring and damper in parallel. The contractile element function of P was determined by the response to a step input in P, using values of spring and damping elements from the perturbation study. The study showed that the resulting coefficient functions of the three-element model describe the dynamic response to the step input of P accurately, indicating that the static perturbation results can be applied to the dynamic case. This model is further validated by accurately predicting the contraction response to a triangular P waveform. All three elements have pressure-dependent coefficients for pressure P in the range 207 < or = P < or = 621 kPa (30 < or = P < or = 90 psi). Studies with a step decrease in P (relaxation of the PM) indicate that the damping element coefficient is smaller during relaxation than contraction.